Parking brake actuating mechanism



Aug. 8, 1961 0. K. KELLEY EI'AL 2,995,215

PARKING BRAKE ACTUATING MECHANISM Filed Nov. 10, 1958 5 Sheets-Sheet 1mvsmons Oliver K. Kelley By Gilbert K. Hause orney Aug. 8, 1961 0. K.KELLEY EI'AL 2,995,215

' PARKING BRAKE ACTUATING MECHANISM Filed-Nov. 10, 1958 s Sheets-Sheet 2INVENTORS Oliver K. Kelley y G 'lberfKHaus X/KQ J Q Their Affor ney g-1951 0. K. KELLEY ETAL 2,995,215

PARKING 5am ACTUATING uacmmrsu Filed Nov. 10, 1958 5 Sheets-Sheet 3INVENTORS Oliver K. Kelley F I g. 7 BY Gilbert K. House Their Afforny vAug. 8, 1961 0. K. KELLEY ETAL 2,995,215

PARKING BRAKE ACTUATING MECHANISM Filed Nov. 10, 1958 5 Sheets-Sheet 4INVENTORS Oi Iver K. Kelley BY GllberfKHause Their Attorney 7 Aug. 8,1961 0. K. KELLEY ETAL 2,995,215

PARKING BRAKE ACTUATING MECHANISM v Filed Nov. 10. 1958 5 Sheets-Sheet 5INVENTORS Oiiver K. Kelley BY Gilbert K. Haui; Tl velr Attorney UnitedStates Patent 2,995,215 PARKING BRAKE ACTUATING MECHANISM Oliver K.Kelley and Gilbert K. Hause, Bloomfield Hills,

Mich, assignors to General Motors Corporation, Detroit, Mich. acorporation of Delaware Filed Nov. 10, 1958. Ser. No. 772,977 3 Claims.(Cl. 188-72) 'This invention relates to a vehicle disk brake and moreparticularly to a parking brake actuating mechanism for a vehiclediskbrake.

One of the problems of operating a parking brake in conjunction with avehicle disk brake has been in providing a parking brake'which providesadequate braking after the friction disks have cooled. If the brakedisks have been in operation for a considerable time prior toapplication of the parking brake, they have a certain amount of axialexpansion due to the heating of the brake disks. With the closetolerances employed between the friction disks, the changing from a hotto a cool temperature is sometimes sufficient to release the brakingefiect provided by the parking brake.

It has been difl'icult to provide a braking mechanism type of brake. Theparking brake must operatewithin this limited space and yet provideadequate braking all conditions.

It is afurther object of this invention to provide a ball groove nut andball groove sleeve which is cable operated to provide axial elongationfor the actuation of a parking brake operating in conjunction with avehicle disk brake.

It is a further object of this invention to provide a cable operatedball groove nut and ball groove sleeve mechanism for axial elongationand operation of a vehicle disk brake. In conjunction with this type ofparking brake, it is further intended that this type of mechanism shouldoperate with a hydraulic annular piston which is used for actuation ofthe regular braking means.

It is a further object to provide a means for adjusting the clearance.between the brake disks automatically during the braking cycle. Thisautomatic adjustment is provided by movable members which have a closefitting tolerance with the annular hydraulic piston where they arefitted into the piston.

These objects are accomplished by a vehicle parking brake actuatingmechanism which operates in conjunction with the vehicle disk brake. Thevehicle disk brake is actuated by an annular hydraulic piston. Thisbydr'aulic piston operates as a ball groove sleeve when actuated by theparking brake mechanism. A ball groove nut is placed concentrically withthe annular piston with a mating helical ball groove which is cutpartially within the nut and partially in the piston sleeve. The ballgroove nut is' rotated by means of a cable. Spherical balls are insertedin the helical ball groove and resiliently held in position by springs.As the ball groove nut is rotated in relation to'the ball groove pistonsleeve, the two members elongate axially in relation to each other.These two members being combined in an enclosure with the piston sleeveabutting the braking disks, and the brakes are actuated when themechanism is elongated.

To give added assistance to the actuation of the park- 'within thelimited space usually present in a vehicle disk 2,995,215 Patented Aug.8, 1961 ing brake, the hydraulic brakes may also be actuated and therebyproviding greater compression of the brake disk stack. With the addedpressure created on the disk stack, the releasing of the brakes uponcooling of the brake disks is quite unlikely.

An added feature is incorporated in this braking structure whereby anautomatic clearance adjustment is built into the braking mechanism. Thisclearance is provided by a closely fitted member projecting into theannular piston. The member moves through a flange in the piston duringbrake actuation and has a clearance between the housing and the memberequal to the clearance between the brake disks. The retraction springsreturn the piston so the member rests on the housing. The member slidesthrough the annular piston at a rate equal to the wear'on the diskstacks.

Further objects and advantages of the present invention will be apparentfrom the following description.

reference being had to the accompanying drawings where-' in a preferredembodiment of the present invention is clearly shown.

FIG. 1 is a crosssection view of the vehicle disk brake in a verticalplane through the center line of the wheel axle. This view also shows aparking brake actuating means.

FIG. 2 is a cross-section view taken on line 2-2 of FIG. 1. This viewshows the end portion of the parking brake actuatingmeans and the cableconnection.

FIG. 3 is a cross-section view taken on line 3-3 of FIG. I. This viewshows a central portion of the parking brake actuating means and themeans for retaining the spherical balls. A portion of the view is cutaway for clarification of the parts.

FIG. 4 is a cross-section view taken on line 4-4 of FIG. 3.

FIG. 5 is a cross-section view taken on line 5-5 of FIG. 3.

FIG. 6 is a cross-section view taken on line 6-6 of FIG. 2.

FIG. 7 is a cross-section view of a modified version of the vehicle diskbrake and parking brake actuating mechanism. The view is taken on aplane vertically through the center line of the wheel shaft.

FIG. 8 is a cross-section view taken on line 8-8 of FIG. 7 showing themounting of the cable. and the spherical ball members between the ballgroove nut and the ball groove sleeve member.

FIG. 9 is a cross-section view of another modification of the emergencybrake actuating means.

FIG. 10 is a cross-section view taken on line 10-10 of FIG. 9.

FIG. 11 is a cross-section view taken on line 11-11 of FIG. 9.

FIG. 1 illustrates thebraking structure and the parking brake actuatingmeans. The cross-section of the wheel is shown at l which is bolted tothe wheel hub 2 by means of bolts 3 and nuts 6. An integral flange ofthe wheel shaft 7 is aligned by means of the dowel pins 4 and connectedto the hub portion 2 by means of bolts 5. The wheel shaft 7 extendsthrough the internal portion of the brake structure and the parkingbrake actuating means. The hub section 2 forms a housing around theouter periphery of the brake disks. A seal 8 is provided between the hub2 and the flange of shaft 7. The rotating disks 9 are mounted on aspline connection on the inis mounted a backing plate 12. On theoutboard side of the braking disks 9 and 10 is mounted a pressure plate13.

A ball bearing assembly 16 is mounted on the inner periphery of the hubsection 2 inboard of the backing plate I 12. This ball bearing assembly16 comprises an outer race 14a, an inner race 14, a ball bearing cage 15and rolling element 15a. A seal 17 is provided on the inner periphery ofthe ball bearing assembly 16. A seal 18 is provided on the outerperiphery of the ball bearing assembly 16 and the inner periphery of thehub 2. An internal seal is provided at 19 between the outer race 14a andthe inner race 14. The inboard side of the ball hearing assembly 16abuts the housing 11 and also a retainer ring 20 which is mounted on theinboard edge of hub 2.

The housing 11 is connected to a shaft housing extension 21 by means ofbolts 22. This housing extension 21 extends inward to the differentialof the vehicle. Within the housing extension 21 is mounted the parkingbrake actuating means. A sleeve member 23 is placed about the driveshaft 7 and extends from a point within the housing extension 21 to theoutboard side of the pressure plate 13. This sleeve member 23 has aradial flange 23a on its outboard end which actuates the disk stack whenthe sleeve is moved axially inward. The inboard end of this sleevereceives a snap ring 24 in a groove about its outer periphery. This snapring 24 abuts the inboard side of the annular wheel piston 25. A seal 26is providcd between the inboard end of the annular fluid piston and theinternal periphery of the housing extension 21. The outboard side of thewheel piston 25 is provided with two seals 27 and 28 which provide apressure chamber for actuating of the disk brake. An inlet fluid passage29 is provided for the actuating fluid. This passage is connected to aduct 30 which extendsto the master cylinder which is operated by thebrake pedal 31.

About .the outer periphery of the annular piston 25 is cut a helicalball groove. This groove has a mating section on the ball groove nut 32.This groove receives spherical balls which move the annular pistonaxially in relation to the ball groove nut 32 as the ball groove nut.

The shaft housing extension 21 has a ball hearing. as scmbly 37 insertedwithin'its inner periphery for receiving the shaft member 7. A seal 38is provided on the ball bearing assemblys outer periphery and a seal 39is dis' posed on the inner periphery of the bearing assembly. A fluidseal 40 is provided between the inner and outer races of the ballbearing assembly 37. This ball bearing assembly abuts a radial flangeportion on the inner periphery of the shaft housing extensions 21. Areturn spring 41 is placed between the ball bearing assembly 37 and theannular piston 25.

The means for providing the proper clearance between the rotating andstationary disks is shown in FIG. 1. The screw member'42 is threadedlyengaged in the shaft housing II. The shoulder portion 43 abuts againstthe rad al flange of the inboard side of the housing extension 11. Thedistance between this shoulder 43 and the head 44 of the screw member 42is a predetermined length. The s eeve member is placed on the screwmember 42 prior in assembling. The difference in length of the sleevemember 45 and the distance between the shoulder 43 and the head 44 isthe predetermined clearance to be provided between the braking disks.The sleeve 45 has a close fitting tolerance on the innerperiphery of thehole 46' of the fluid piston 25 in which it is inserted.

I-it i. 2 is a crmsscction view showing the end portion of the parkingbrake actuating means. The housing extension 21 is mountedconcentrically around the ball groove nut 32. The extension housing 21is also shown extending within the ball groove nut 32. A coil spring 50is located concentrically within these two portions of the shaft housingextension 21. The one end of spring 50 has a radialy extending portion51 which engages a portion ofthe ball groove nut 32. The opposite end ofthis coil spring extends axially outboard into the annular wheel piston25. This end of the spring 52 is shown inscrted in a hole of the annularpiston 25 by FIG. 6.

The actuating sleeve 23 is shown concentrically mounted about the wheelshaft 7. The cable 53 is connected to axially extending flanges 54 and55. The cable 53 is wound around the flange 54 and then doubled backbetween the two similarly shaped-flanges on the ball groove nut 32. Thiscable wraps around the outer periphery of the ball groove nut 32 andextends outward through a cable fitting of the shaft housing extension21.

The cable fitting comprises a sleeve 56 which is inserted in the shafthousing extension 21. Within the inner periphery of the sleeve 56 ismounted a cable guide 57 which has a seal member 58 about its outerperiphery and the inner periphery of the sleeve 56. The cable guide 57is held in position by means of a threaded sleeve which engages theinner periphery of the outer end of sleeve 56. The cable 53' extendsinto an armoured portion 59 on the outer side of the cable fitting.About the outer periphery of the armoured portion 59a spring is providedwhich is also shown at 60. I

FIG. 3 is a cross-section view of the cable actuated parking brakemechanism. This view illustrates the mounting of the spherical balls 61within the mating ball grooves. A pin 62 is mounted on the hydraulicpiston 25 adjacent the end of the spherical balls 61. The pin 63 ismounted in the ball groove nut 32 adjacent the spring 64. This springextends from the pin 63 in the annular ball groove to the adjacent endof the spherical balls 61. The mounting of the pin 62 is also shown inFIG. 4. The groove 33 in the ball groove nut 32 is also shown in FIG. 4.This groove receives the spherical ball 34.

FIG. 7 is a modified version of the parking brake actuating mechanism.The hub or wheel mounting flange is shown at 70 as an integral part ofthe shaft 71. The shaft 71 is rotatably mounted within the brake housing72 which receives the ball bearing assembly 73. The ball bearingassembly 73 is retained in position by the annular flange member 74which is held in place by the bolts 75.

A seal member 76 is placed on the outer periphery of the ball bearingassembly 73. A second seal 77 is also placed on the inner periphery ofthe ball bearing assembly 73. The brake housing 72 is mounted adjacentto the wheel cylinder 78 and held in position by bolts 79. A seal 80 isprovided between the brake housing 72 and wheel cylinder 78. On theinboard side of the wheel cylinder 78. a shaft housing 81 is bolted bymeans of bolts 82. The ball bearing assembly 83 is inserted within shafthousing 81. A seal member 84 is placed between the shaft 71 and the ballbearing assembly 83. A seal 85 is placed between the shaft housing 81and the ball bearing assembly 83. A seal 86 is also placed between theinner and outer races of the ball bearing assembly 83.

The modification of the brake assembly employs an annular piston whichmoves axially outboard to actuate the brakes. The brake housing 72operates as the pressure plate for the disk stack. The rotating disks 87are mounted on a spline portion of shaft 71. These rotating disks 87 areprovided with a friction material for engaging the stator disks 88. Thestator disks 88 are mounted on pins 89 which fit into aligned holes inthe brake housing 72 and the wheel cylinder 78. A seal 90 is providedbetween the brake housing 72 and the wheel cylinder 78. The fluidactuating chamber for the hydraulic annular piston is shown at 91. Theseal 92 at the outboard end and the seal 93 at the inboard end confinethe fluid within the actuating chamber 91.

The annular piston 191 is held in a nonrotating position by means of thepin 89. These pins 89 are spaced about the outboard side of the wheelcylinder 78. Alternately spaced between these pins 89 are the clearanceadjusting devices. These devices comprise pins 94 which are mounted inclosely fitted holes in the radially outer portion of the annular piston191. As the braking disks become worn, the annular piston 191 ispermitted to move a greater distance outboard and the pins 94 are movedwithin the annular piston. The movement of the pins 94 is in a directrelation to the wear of the brake disks. The annular piston 191 isreturned to its normal position upon release of the brakes by the returnsprings 95. The inboard end of the pins 94 determine the retractedposition of the piston 191.

The annular piston has a helical ball groove about its inner peripheryon the inboard end. A ball groove nut 96 has a mating ball groove aboutits outer periphery on its outboard end. Spherical balls 97 are placedwithin the mating portions of the ball groove portion of the fluidpiston and the ball groove portion of the nut 96. As the ball groove nut96 is rotated, a pressure is created on the groove 98 on the inboardside of nut 96. The groove 98 has a mating portion on the annularshoulder member 99 for receiving spherical balls 100. Upon rotation ofthe ball groove nut 96 the annular piston is moved axially outboard bythe force created on the spherical balls 97 within theirhelical groove.The outboard axial movement of the piston 191 creates engagement of thebraking disks.

FIGURE 8 illustrates a cross-section portion of the parking brakeactuating means. The wheel cylinder 78 with its attaching bolts 79 isshown around the outer periphery of the rotating portion of the brakemechanism. The wheel cylinder 78 encloses the rotating mechanism andprovides a seating portion for the annular shoulder member 99 with anannular groove for receiving the balls 100. The spherical balls 100 areplaced between the ball groove nut 96 and the annular shoulder 99. Theannular shoulder member 99 is in a non-rotating position on the wheelcylinder 78. The ball groove nut 96 is rotatably mounted on thespherical balls 97. The cable 105 extends inward within the housing andis attached to a ball 106 which is fitted into a slot 107 in the ballgroove nut 96. The cable 105 extends outward from the housing portionthrough a cable guide 108.

The cable guide 108 is fixed in position by means of a pin 109 and isprovided with a seal 110 on its inner end.

The outer end of the cable guide is received within an extended portionof the cable guide 111 which carries an armored portion 112 about itsinner periphery. The cable 105 extends outwardly where it is attached toa handle member 113 which is used for actuating the parking brakingmechanism. The handle member 113 is provided with a ratchet portion 114which engages the pawl 115 which locks the ratchet arm 114 uponactuation of the braking mechanism.

FIGS. 9, l0, and 11 illustrate a modification of the parking brakemechanism. FIG. 9 is taken through the center line of the wheel shaft ina vertical plane. The wheel cylinder 116 is shown connected to the shafthousing 117 by means of bolts 118 and washers 119. A seal 120 is shownbetween the wheel cylinder 116 and shaft housing 117. The shaft 121 isrotatably mounted within the ball bearing assembly 122 which is mountedon the inner periphery of the shaft housing 117. A fluid seal assembly124 is mounted adjacent the ball bearing assembly. The annular wheelpiston 125 is mounted within the wheel cylinder 116. A needle bearingassembly 126 is mounted axially inboard from the annular piston 125.This needle bearing assembly 126 is mounted adjacent the ball groove nut127 which has a helical ball groove on its inner periphery. A ballgroovesleeve 128 is mounted within the inner periphery of the ballgroove nut 127 and has a mating helical ball groove on its outerperiphery. Spherical balls 129 are retained within the mating portion ofthe helical ball groove nut 127 and ball groove sleeve 128. I

A cable 130 is wrapped around the outer periphery of the ball groove nut127. On the inboard side of the ball groove nut 127 is mounted aresilient spring 132 for returning the brake actuating means after themechanism has been released. A pin 131 is mounted within housing 116 andfunctions as a stop means which abuts against the one end of the returnspring 132 mounted within the housing 116 and abutting the pin 131. Thespring 132 extends about the inner periphery of the housing 116 to whereit abuts two pins 133 and 134 at the opposite end of spring 132. It willbe noted that the flange portion 135 which is a portion of the ballgroove nut 127 is shown abutting this spring 132. This view shows thebraking mechanism in the return position. This flange portion 135 isalso illustrated in FIG. 9 as a portion of the ball groove nut 127. FIG.11 also shows a portion of the annular hydraulic piston which isconcentrically mounted around the shaft 121.

The attaching means for the cable are illustrated in FIG. 10. A portion136 of the ball groove nut 127 extends radially outward from the ballgroove nut. The cable 130 extends tangentially around the ball groovenuet and through the portion 136 where it is attached to a ball 137which locks the cable in position. As the outer portion of the cable ispulled, the ball 137 creates a pressure against the radial flange 136and thereby rotates the ball groove nut 127.

This cable is also provided with a guide means on its outer end. Thisguide means is generally of the same structure previously described. Theball groove nut is shown rotatably mounted on the spherical balls 129.These balls are mounted on a helical mating groove on the internalgroove sleeve 128. The shaft 121 is shown concentrically mounted withinthe ball groove sleeve 128. The operation and assembly of this ballgroove sleeve is of the general structure previously described in thepreceding paragraphs of the other modifications.

The parking brake actuating mechanism operates in this manner: Referringto views 1 and 2, as the cable 53 is pulled outward for the actuation ofthe brakes, the ball groove nut 32 is rotated. The annular piston 25which is mounted concentrically within ball groove nut 32 has matingball grooves for receiving the spherical balls 61. As the ball groovenut is rotated in relation to the hydraulic piston 25, the hydraulicpiston moves axially inboard. This axially inboard movement of thehydraulic piston 25 continues until the flange portion 23a of sleeve 23compresses the pressure plate 13 against the brake disk stack. As thebrake disks 9 and 10 frictionally engage each other, the rotation of thevehicle wheel 1 is retarded. I

The force on the flange 2311 on the wheel portion 25 creates a reactionforce through the spherical balls 61 onto the ball groove nut 32. Thisforce is transmitted through the spherical balls 34 and transmitted tothe shaft housing 11.

This brake has the added feature of being assisted by the hydraulicsystem for actuating the brakes. This feature is an advantage in eventthat the brake disks are hot from constant use. The heat within thebraking structure causes an expansion of the brake disks which may causea release of the brakes if they are not actuated firmly. This brake.having a high mechanical advantage in the screw arrangement of the ballgroove nut. would not generally necessitate the use of the hydraulicfluid system, but in event that the operator should desire to use thisassisting force, the actuating of the wheel cylinder is in the samedirection in cooperation with the hand operating means.

The brake actuation by the foot pedal 31 displaces fluid within themaster cylinder 30a which creates a pressurized fluid within theactuating chamber of the housing 11 and piston 25.

Upon release of the brakes either by the hydraulic actuating means orthe manual parking brake mechanism, the return spring 41 returns thepiston 25 to its retracted position. I

The brake actuating mechanism has a built-in clearance adjustment forthe brake disks. This adjustment is providedfor in this manner: A screwmember 42 is mounted concentrically within sleeve member 45 on theradial flange of the housing member-11. These screws are angularlyspaced about the radial flange on a common radial circle'of the housingmember 11. The sleeve member 45 is snugly fitted within the reamed holeof the hydraulic wheel piston 25. The screw 42 is screwed snugly againstthe flange portion of the housing member 11 with the shoulder 43abutting the flange portion of housing 11. The predetermined clearancewhich is to be provided between the brake disks is equal to thedifference in length of the distance from the shoulder portion 43 to thehead 44 of screws 42 and the length of sleeve 45.

As the hydraulic annular piston 25 is actuated. the piston 25 movesinboard carrying the'sleeve 45. If excessive clearance exists betweenthe brake disks, the sleeve 45 will abut the head 44 and the head willslide sleeve 45 axially outboard in the annular hydraulic piston 25. Asthe brakes are released. the annular piston moves outboard carrying thesleeve 45 to a new position. The

annular piston 25 does not completely return'to its orig:

inal position, but only to the point-where the Outboard edge of the seeve 45 abuts the radial flange portion of the housing II. By thismeans. a constant clearance is provided between the braking .disks. Thismeans that the annular cylinder will move a constant distance for brakeactuation whether it be by the hydraulic fluid system or the parkingbrake actuation means. r

The version illustrated in FIG. 7 operates in the same manner-as theoriginal version of this brake actuating means. except the hydraulicwheel piston 191 and the ball groove nut 96 elongate, and the ballgroove nut forces against the annular member 99 into the spherical ballsI00. -A"torsion spring 51 is provided for returning the ball groove nutto its original position.

The modification illustrated in views 9. l and 11 operates on the ballgroove principal with a ball groove nut and ball groove sleeve except aneedle bearing assembly 126 is placed between the ball groove nut 127and the hydraulic wheel piston 125. The return means for the parkingbrake actuating mechanism utilizes the comprcssion coil spring insteadof the torsion-type spring. which is mounted concentrically around thewheel shaft.

While the embodiment .of the present invention as herein d sclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows: v

- l. A parking brake actuating mechanism comprising in combination. ahousing means, a shaft means rotatably mounted within said housingmeans, a wheel attached to suizl shaft means. one or more rotating disksmounted on said shaf t means. stator disks mounted on said housinq:means. an annular hydraulic wheel cylinder for friction-Hy engaging saidbraking disks with each other by prcssuriacd fluid in said brakingsystem, a ball groove nut munntcd concentrically with said annularhydraulic cylinder. a: helical ball groove on said'hydraulic wheelcylinder and mating helical ball groove on said ball groove nut forreception of spherical balls, a cable connected to said ball groove nutfor rotating said ball groo e nut in relation to said hydraulic'wheelcylinder and thereby providing relative axial movement and actuation ofsaid brake disk. a torsion spring for returning said ball groove nut toits normal position, alignment pins for aligning the hydraulic wheelcylinder in a nonrotating position in relation to said housing means.clearance adjusting pins alternately spaced in said wheel cylinder,return springs mounted on said adjusting pins. said adjusting pins beingof a predetermined shorter length than the spaced portion within thehousing means 8 which they are located, said difference in length of thepins and the spaced portion in the housing means being the predeterminedclearance to be provided between the braking disks, said spaceautomatically adjusted upon actuation of said wheel cylinder during theactuation of said brakes.

2. A parking brake actuating means comprising in combination, a housingmeans, a shaft means rotat-ably mounted within said housing means, awheel connected to said shaft, one or more rotator disks connected tosaid shaft means, one or more stator disks connected to said housingmeans, an annular hydraulic wheel cylinder for frictionally engagingsaid stator disks with said rotator disks, a ball groove nut mountedconcentrically with said annular hydraulic wheel cylinder, helical ballgrooves on said annular, wheel cylinder and helical mating ball grooveson said ball groove nut for reception of spherical balls fortransmission of an axial force from said ball groove nut to said annularhydraulic wheel cylinder when said members are rotated in relation toeach other,

alignment pins mounted in said housing means for retaining non-rotativealignment between said housing means and said annular hydrauliccylinder, adjusting pins abutting the housing means and mounted with aclosely fitted tolerance in said annular hydraulic cylinder with returnsprings concentrically mounted about said adjusting pins, said adjustingpins of a predetermined shorter length than the spaced portion withinsaid housing means which they are located, said predetermined shorterlength being the spaced'clearance between saidrotator apd stator disks,said clearance adjustment being automatically maintained as said wheelcylinder is operated for the actuation of said brakes.

3. A parking brake actuating mechanism comprising in combination, ahousing means, a shaft means rotatably mounted within said housingmeans, a wheel connected to said shaft means, one or more rotatingdisksconnected to said shaft means, one or more stator disks connected tosaid housing means, a hydraulic annular cylinder mounted within saidhousing means having a hydraulic chamber for frictionally engaging ofsaid brake disks, a ball groove nut concentrically mounted with saidannular hydraulic cylinder, a helical ball groove on said annularhydraulic cylinder and a mating helical ball groove on said ball groovenut for reception of spherical balls for transmission of an axial forcefrom said ball groove nut to said annular hydraulic cylinder when saidmembers are rotated in relation to each other, a cable means forrotating said ball groove nut and a means for pressurizing fluid in saidfluid chamber of said hydraulic cylinder. thereby providing twosimultaneous means for actuating'said braking means, alignment pinsmounted in said housing member for maintaining said hydraulic ReferencesCited in the file of this patent UNITED STATES PATENTS 1,791,685Rockwell et al Feb. 10, 1931 2,014,630 OBrien et a1. Sept. 17, 19352,091,268 Colman Aug. 31, 1937 2,115,661 Zima Apr. 26. 1938 2,384,297Goepfrich Sept. 4, 1945 2,914,142

Klaue Nov. 24, 1959

